Non-contact ignition device



Feb. 6, 1968 YOSHIAKI HIROSAWA ETAL 3,367,314

NONCONTACT IGNITION DEVICE Filed Sept. 8. 1965 United States Patent3,367,314 NON-CONTACT IGNITION DEVICE Yoshiald Hirosawa, Tokyo, TakayaSenzaki, Yamatomachi, Kita-adachi-gun, Saitarna Prefecture, Japan,assignors to Kahushilri Kaislia Honda Gijutsu Kenkyusho, SaitamaPrefecture, Japan, a corporation of Japan Filed Sept. 8, 1965, Ser. No.485,859

Claims priority, application Japan, Sept. 16, 1964,

int/52,993

3 Claims. (Cl. 123-148) ABSTRACT OF THE DISCLOSURE The inventioncomprises an electrical ignition system for internal combustion engineswherein an A.C. generator source charges a condenser through half-waverectifier means and an SCR is switched on to discharge the condenser viathe primary ignition coil thereby producing a firing spark. Theswitching circuit for the SCR comprises a constant voltage diode and aresistor connected in series therewith, the combination being inparallel with the SCR. A connection from the junction of the diode andresistor extends to the gate of the SCR so that when a predeterminedvoltage level in the half-wave signal is reached, the diode currentcauses a pulse to the gate for firing the SCR which in turn provides thedischarge path for the condenser.

This invention relates to a non-contact ignition device for internalcombustion engines, wherein the charging and discharging of condenser,as well as the switching of semiconductor elements are utilized.

More particularly the present invention relates to the type ofnon-contact ignition device wherein an output current of an A.C.generator, such as a magneto generator, which is rotated synchronouslywith the internal combustion engine, is rectified to charge a condenserand the charged condenser is discharged by means of a switching circuitcomprising a silicon controlled rectifier (which hereinafter isabbreviated to SCR) through a primary coil of the ignition coils so thathigh voltage or tension induced in a secondary coil may be applied to aplug.

A first object of the present invention is to provide an improvednon-contact ignition device of the type referred to above wherein aseparate or further generator, synchronized with said first mentionedgenerator as means for feeding a positive signal current to the gate ofthe SCR,

is eliminated because the condenser or capacitor is discharged byactuating the SCR switching circuit in synchronism with the rotation ofthe output shaft of the internal combustion engine.

A second object of the present invention is to provide such a devicewherein the time when said signal gate current is supplied, that is, thetime for igniting can be easily controlled, which object may be achievedconcurrently with said first object.

A third object is to provide such a device wherein the pulse circuit inthe condenser charging and discharging type ignition device foraccomplishing the foregoing objects may be easily constructed.

Further features and advantages of the present invention will be clearfrom the following explanation of the invention in detail in connectionwith the accompanying drawings, in which:

FIG. 1 is a connection diagram of the circuit according to the presentinvention; and

FIG. 2 shows the operational characteristics of the constant voltagediode according to the present invention,

Patented Feb. 6, 1968 wherein time is represented along the abscissa andvoltage along the ordinate.

Referring to an embodiment of this invention as illustrated in thedrawings, an alternative-current generator 1, such as a magnetogenerator, is mechanically connected with the output shaft of aninternal combustion engine. A half-wave rectifier 2 is connected togenerator 1 for rectifying its A.C. output. A condenser or capacitor 3is connected in parallel with generator 1. A primary coil 4 and asecondary high tension coil 5 comprises the ignition coils. Asemiconductor controlled rectifier 6 (SCR) provides the discharge pathfor capacitor 3.

The gate G of said SCR 6 is supplied with pulses, so as to discharge thecondenser 3 synchronously with rotation of the internal combustionengine, and induce high tension or voltage in the secondary coil 5, inorder to ignite a plug 7.

It is well known to use another signal generator rotating synchronouslywith the generator 1 as means for getting the gate signal. It is,however, uneconomical to provide two generators.

The present invention eliminates, the additional generator andaccomplishes the same purpose with a simple circuit construction. Aconstant voltage diode 8 is electrically connected between an anode A ofthe SCR 6 and the gate G. When the voltage at the anode reaches at acertain or predetermined level, an ignition gate signal is given to thegate G by Zener current from the constant voltage diode 8 so as to turnon SCR 6. A resistor 9 is connected in series between the constantvoltage diode 3 and earth E or the common return line.

The A.C. output from the generator 1 is rectified by the rectifier 2, sothat the condenser or capacitor 3 is charged, and simultaneously,equivalent voltages are applied to the anode A of SCR and also to theconstant voltage diode 8. When the anode potential V is reached, apredetermined Zener voltage in the constant voltage diode 8 as shown inFIG. 2, causes the Zener current suddenly to flow through the resistor9. SCR 6 is turned-on by appropriately selecting the current passingthrough the :gate G by the resulting fall of voltage so as to dischargethe charged potential of the condenser 3 through the primary coil 4.When the time t (FIG. 2) has elapsed during the discharge, SCR 6 isturned off. The above-mentioned operation is repeated per each cycle ofoutput current from the generator 1.

In the present invention the ignition is performed synchronously withthe rotation of the internal combustion engine. Thus, with increase ofr.p.m. of the internal combustion engine, the frequency of out-putcurrent of the generator correspondingly increases which is shown inbroken curve V in FIG. 2. It will be clear that the control of ignitiontime may be easily effected by regulating the resistance value of theresistor 9 and consequently the current passing the gate G iscorrespondingly controlled so as to adjust the turning-on time of SCR.

In lieu of the constant voltage diode 8, a resistor may be theoreticallyused. However, due to high power consumption and the difficulty ofcharging the condenser up to a sufliciently high potential and furtheras the operation is unstable and the sparking energy is low, and soforth, the use of a resistor replacement for diode 8 is impractical forthis purpose.

What is claimed:

1. A non-contact ignition device comprising an A.C. generator includingan output circuit, a half-wave rectifier connected in the output circuitof said generator, a primary ignition coil and a silicon controlledrectifier having an anode and a cathode and a gate, the anode-cathodebeing connected in series with rectifier, a condenser connected betweenthe half-wave rectifier and the primary coil in parallel with saidsilicon controlled rectifier, a secondary coil coupled to the primarycoil for producing a spark upon condenser discharge a constant voltagediode, a resistor connected in series with said diode, and said diodeand resistor being connected in parallel with the anode-cathode of thesilicon controlled rectifier, and a connection from the junction of theresistor and diode to said gate.

2. An ignition system for an internal combustion engine operative fromthe engine output shaft comprising, in combination A.C. generator means,means connected to the generator for half-wave rectifying the A.C.output, condenser means connected in parallel with the generator meansto be charged by the rectified output, an SCR having an anode and acathode and a gate, a primary ignition coil, said coil and the anode andcathode of the SCR being connected in series with the rectifying means,secondary ignition coil means for developing a high voltage dischargeupon discharge of the condenser means, a switching circuit for the SCR,said circuit comprising a constant voltage diode and a resistorconnected in series, and a connection from between the diode andresistor to the gate for supplying a pulse to the gate to turn the SCRReferences Cited UNITED STATES PATENTS 2,030,228 2/1936 Randolph et a1123148 2,071,573 2/1937 Randolph et al 123148 2,151,796 3/1939 Peters123148 2,203,579 6/1940 Randolph 123148 OTHER REFERENCES Solid StateProducts Incorporation, One Pingres St. Salem, Mass, Bulletin D 420-02,August 1959, pages 17-18 (Figure 27).

Solid State Products Incorporation, Bulletin D 4211-02, September 1960,pages 15 and 16 (Figure 22).

20 LAURENCE M. GOODRIDGE, Primary Examiner.

